Preheat your oven to 350째F (175째C).
Grease and flour a 9-inch round cake pan.
In a large mixing bowl, beat the eggs and sugar together until light and fluffy.
Sift the flour and baking powder together, then fold into the egg mixture.
Heat the milk and melted butter together until warm, then gently fold into the batter.
Pour the batter into the prepared cake pan and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool completely on a wire rack.
In a saucepan, heat the milk and vanilla bean (if using) until just boiling. Remove from heat and let steep for 10 minutes. If using vanilla extract, add it later.
In a bowl, whisk together the egg yolks, sugar, and cornstarch until smooth.
Gradually pour the hot milk into the egg mixture, whisking constantly.
Return the mixture to the saucepan and cook over medium heat, stirring constantly, until thickened.
Remove from heat and stir in the butter and vanilla extract (if using).
Allow the pastry cream to cool completely.
In a large mixing bowl, beat the heavy cream, powdered sugar, and vanilla extract together until stiff peaks form.
Slice the cooled sponge cake into three even layers.
Place the bottom layer on a cake plate and spread with a thin layer of raspberry jam.
Spread a layer of pastry cream over the jam.
Add the second layer of cake and repeat with another layer of jam and pastry cream.
Place the final layer of cake on top.
Cover the entire cake with a thick layer of whipped cream, shaping it into a dome.
Knead a few drops of green food coloring into the marzipan until evenly colored.
Dust a clean surface with powdered sugar and roll out the marzipan into a large circle, about 1/8 inch thick.
Carefully drape the marzipan over the cake, smoothing it down and trimming any excess.
If desired, place a pink marzipan rose on top for decoration.
Dust the finished cake with powdered sugar.
Enjoy your meal!